Method of forming coils



Oct, 19, 1965 R. 1.. DAVIS, JR

METHOD OF FORMING COILS 2 Sheets-Sheet 1 Filed Dec. 18, 1961 Oct. 19, 1965 R. L. DAVIS, JR

METHOD OF FORMING COILS 2 Sheets-Sheet 2 Filed Dec. 18, 1961 United States Patent 3,212,172 METHOD OF FORMING COILS Reuel L. Davis, Jr., Dover, N.H., assignor to General Electric Company, a corporation of New York Filed Dec. 18, 1961, Ser. No. 160,171 1 Claim. '(Cl. 29-155.57)

This invention relates to coils such as transformer coils and the like, and more particularly to a method of forming such coils and the coils which are formed by such method.

It is well known in the coil making art to wind coils for use in transformers or the like electrical apparatus on some type of a winding form. In general, the coil is wound in layers along the form, the wire from one end of each layer usually being returned to the beginning of the lower layer and the next layer being wound in the same direction as this lower layer. Due to the voltage drop through the wire, when the coil is utilized in electrical apparatus and such apparatus is energized, a voltage gradient or difference is developed between adjacent turns in adjacent layers of the coil. That is, a voltage gradient is developed between the first turn in one layer, such as a lower layer, and the last turn in the next adjacent or upper layer. This voltage gradient, during the use of the coil, is generally substantially greater than the voltage gradient between adjacent turns in a single layer of the coil. In winding such coils, it is usual to use an insulated wire, the insulation of the wire being sufiicient to protect the adjacent turns from the voltage gradient developed therebetween, but it is not suflicient to provide 7 the necessary insulation between the different layers of the coil. In order to provide the necessary insulation between adjacent layers, it has been the general practice in the coil winding art to provide paper insulation, or the like, between the different layers of the coil. A construction of this type is disclosed, for example, in Patent No. 2,985,950.

As will be understood this type of construction is relatively expensive, both from the standpoint of materials used, and from the time and labor which is necessary to construct the coil. Further, as will be understood, coils which have been constructed in this manner are dependout upon their layer insulation to prevent breakdown between the layers when the coils are subjected to high impulse voltages. It will be understood that impulse voltages are large voltages which are suddenly impressed on the electrical apparatus and which substantially increase the voltage gradient between layers of the coil over that existing during steady state normal operating condition. As is well known, any weakness in the layer insulation or the subsequent deterioration of the layer insulation during use of the coil will result in short circuits developing between various layers of the coil from impulse voltages, or from normal operating voltages,

which will eventually cause the breakdown of the coil.

It has long been recognized as desirable to provide coils which are wound of insulated wire in which the various layer insulation could be eliminated, that is, it has been recognized as desirable to make coils in which all the turns of the coil are contiguous to all the turns which are adjacent thereto. As used throughout the specification and claims, the term contiguous, when relating to turns, will mean that the adjacent turns are in substantial contact with each other, and that no additional insulation is provided between such adjacent turns. It has generally been considered impractical to provide coils in which all the turns are contiguous to all adjacent turns thereto because of the commercial and economic problems involved. As will be understood, the amount of insulation which would be necessary on each turn of Patented Oct. 19, 1965 the wire, to provide the necessary insulation for the voltage gradient between layers, would make the wire extremely expensive, while at the same time increasing the overall size of the coil such that the overall dimension of a coil formed therefrom would be substantially larger than present day coils which are formed from the usual insulated wire and provided with layer insulation between the various layers of the wire.

It is therefore one object of this invention to provide a new and novel method of making a coil where the use of layer insulation has been eliminated.

A further object of this invention is to provide a novel economical coil, wherein all turns of the coil are contiguous to all adjacent turns.

A still further object of this invention is to provide a new and novel method of making a coil in which the turns of the coil are randomly wound from one end of the coil to the other, in substantially the same manner, as the applied voltage progresses across the coil.

It is a further object of this invention to provide a novel, randomly wound coil.

In carrying out this invention in one form, a coil is provided in which the various turns of the coils are randomly wound with all turns of such coil being contiguous to all adjacent turns. The coil is made by the method of providing a cavity, such as a mold or the like, in the shape desired for the specific coil, and then randomly spinning or otherwise laying turns of wire into such cavity. After the cavity is filled with wire the wire is compacted, in any desired manner, within the cavity to form atight, randomly wound coil. The formed coil may then be encapsulated with any desired type of insulating material, or taped to provide a solid, randomly wound coil. v

The invention which is sought to be protected will be particularly pointed out in the claims which are appended hereto. However, it is believed that this invention and the manner in which its various objects are obtained, as well as other objects and advantages, will be better understood from the following description when taken in connection with the accompanying drawings, in which:

FIGURE 1 is a perspective view of of a transformer, partly in section, showing one use of the novel coil of this invention;

FIGURE 2 is a top view of one form of cavity which may be used in making the coil of this invention, showing one method of placing the wire forming the coil into such cavity; I

FIGURE 3 is a sectional view taken substantially along the line 3-3 of FIG. '2 and showing one method of compacting which may be used in the method of this invention;

FIGURE 4 is a schematic representation of one means of encapsulating the formed coil made by the method of this invention; and

FIGURE 5 is a side view of a finished coil, partly in section, made according to this invention.

Referring now to the drawings, in which like numerals are used to indicate like parts throughout, and referring specifically to- FIG. 1, there is shown an instrument transformer, for example a potential transformer 10, provided with a primary and secondary coil and a core, in a manner well known to those skilled in the art. The potential transformer is shown as broken away in one side of the casing 12 thereof to show a section of a randomly wound coil 14 which may be made according to the method of this invention. As will be understood, the coil 14 is the primary coil of the potential transformer 10, and is provided with the voltage of the line to be measured through leads which terminate at connecting points 16, 17 shown on top of the transformer 10. Inasmuch as the primary coil '14 issubiected to the high primary voltage being measured, it will be understood, that the voltage gradient which could be developed between layers, were a substantial number of turns provided in'each layer, would be relatively large and, therefore, it would be necessary to provide layer insulation between the various layers to prevent this voltage gradient from breaking down the insulation which-is provided about each of the turns of the coil. In a mannerhereinafter specified, the use of the layer insulation is eliminated by winding the coil randomly from one end to the other in substantially the same manner as the applied voltage progresses across suchcoil' By means of a coil wound in this fashion, each adjacent 'turn is sub stantially subjected only to the voltage gradient of the normal turn-to-turn volt-age gradient, and thenefo-w, the need for layer insulation has been completely eliminated.

Referring now to FIGS. 2 a nd 3 of the drawings, one method of making the randomly Wound coil of this 'invention will be described. As shown in FIGS. 2 and 3, a cavity 18 is provided, the cavity being formed in any desired shape, a rectangular shape being shown in this instance. 'T he cavity is formed in a mold 20, which has a base 21 and an upstanding central member 22, by placinga central winding member 24 over the mold center member 22 and a winding can 2 6 within the outer upstanding member 28 of the mold 20. Thus, the cavity 18 comprises portions of theinner surface of the base 21 of the mold 20, the outside'surface of the central winding member 24 and the inside surface of the winding can 26. The central winding member 24 and the winding can. 26 are shown as fitting, closely againsttheadjacent surfaces of the central member 22 and'the outer member 28. Of course, it will be understood that these may fit as snugly or loosely as desired, since the central winding member 24 and the winding can are used 'as spacer and winding members as will be more clearly described 'hereaften Further, an opening. 30 is provided in both the winding After the compacting step has been provided, for example by means of the press 45 indicated in FIG. 3, the formed coil Within the mold 20 may then be placed in an encapsulating machine, such as, for example, machine 48 shown in FIG. 4. As will be understood, before the mold is placed into the encapsulating machine 48 the center piece 24 and the winding can 26 are removed. In

1 asmuch as the coil has been firmly compacted it will maintain its shape, thereby leaving spaces between the center piece 22 and the upstanding outer portion 28 of the mold 20 and the formed coil, such that the encapsulating material may be brought into the mold on each side of the formed coil. As indicated in FIG. 4, after the mold with the formed coil is placed into the encapsulating machine 48 the top 50 is placed thereon and hermetically sealed thereto, for example, by means of bolts 52. A vacuum is then formed within the machine 48 by means of a vacuum pump (not shown) which removes the air from within the machine 48 through the Vacuum pipe 54. After a sufficient vacuum has been obtained within the machine 48, the encapsulating material is caused to flow into the machine by means of the tube 56. The encapsulating mate-rial flows through the tube 56 and into the mold 20 a sindicated, to surround the formed coil and fill all the voids within the mold 20. After a sufficient amount of encapsulating material has been poured into the mold 20 so as to completely surround the formed coil,

' the encapsulating material is stopped and heatis then applied, as necessary, to cure the encapsulating material to thereby firmly encase the coil within such encapsulating material.

As shown in FIG. 5, after the encapsulating material has been cured the coil may be removed from the mold and can 26 and the upstandingportion 28 of the mold 20, such that the end of the wire to be used to form the coil may be taken outside of the mold 20, in the'manne r indicated in FIG. 3. V

The assembled mold, with the center section 24 and the winding can 26 in place thereon, is then placed into a winding machine, such as machine 32, which is provided with a reel of wire 33 mounted in the member 34. The winding wire extends from the member 34 along station-1 ary arm 36, and to a rotary feeding member 38 on the movable arm 40. The winding machine is indicated only in a schematic manner in the drawing since it does notitself form any part of the invention of this application. As indicated in FIG. 2, the wire isfed from thefeeding member 38 on movable arm 40 into the cavity 18 formed in the mold 20. The movable arm 40 is caused to move in a lateral and oscillatory manner about the pivot point 42, so as tolay the wire,44 within the cavity 18.

After a suflicient quantity of wire has been randomly wound into the cavity 18 by means of the winding-machine 32, generally up to-the height of the winding can 26 and the center piece 24, as indicated in FIG. 3, the machine is stopped and the mold is removed to a press, suchas press schematically indicated in FIG. 3. In the press 45 a ram member 46 is moved into contact with the winding wire 44 while mold 20 is supported on member 47 of press 45 and causes the wire to be forced tightly into the cavity 18, thereby solidly compacting the winding to form a coil which is substantially the height of the mold 20. This is indicated by the dotted lines in FIG. 3. As will be understood, inasmuch as the wire is randomly wound within the cavity 18, the various turns of wire do not lay on top of each other in the manner usuallyfound in a coil, but they are randomly dispersed at various angles throughout the entire coil in the manner. indicated in FIG. 2. After the compactinglstep this random winding aidsin supportingthe ccilin the same shape in which it has been formed,

will thereby provide a solid, well insulated coil 58 which is randomly wound from the wire 44. The coil 58 does not have any layer insulation and will easily Withstand the voltage gradients which may be caused within such coil when subjected to impulse voltages in use. In FIG. 5

the coil member 58 is shown as being provided with. two separate cores 60 and 62, shown in phantom view, which are inserted Within the window opening 64 of the coil, the window opening of course having been formed when the coil was made by the center piece 22 of the mold 20.

Also as shown in FIG. 5, the lower end of the Wire 44 forming the coil 58 is brought out through the base of the member as shown in the mold in FIG. 3, and forms one terminal 66 of the coil 58 while a second lead 68 from the top end of the coil forms the other terminal of the coil. From the above it will be clear that by means of this invention a randomly wound coil has been provided in which the windings of the coil progress in a random fashion from one end of the coil to the other in substantially the same manner in which the applied voltage progresses across the coil. Also as will be understood, therehas been disclosed a preferred method of constructing the random Wound coil.

While the preferred method of constructing the coil has been described in this specification, it will be understood by those skilled in the art that various changes may be made in such method without departing from the scope of this invention. For example, any type of machine may be provided for laying the wire into the cavity or, if desired, it could even be done by hand. Further, the compacting of the coil may be provided in any desired manner, as by using a press constructed in any desired manner. Further, while the coil of this invention has been shown as being encapsulated, after form-:

ing, in an insulating material, it will be obvious to those skilled in the art that depending upon the use desired of the coil, the coil may be merely provided with a supportscope of the invention is considered only as limited in the manner set forth in the claim appended hereto.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. A method of making a coil comprising the steps (a) providing a mold of substantially the size and shape of the desired coil,

(b) inserting spacers within said mold to form therebetween a cavity,

(c) randomly spinning within said cavity a suflicient number of continuous turns of wire to form a coil with the desired properties,

(d) compacting said wire turns within said cavity to form a compact, randomly wound coil,

(e) removing said spacers from said mold,

(f) placing said mold in an encapsulating machine, and filling the spaces Within said mold about said ing material, and

(g) cur-ing said encapsulating material.

References Cited by the Examiner UNITED STATES PATENTS Keller 29-1555 Chase 336-190 Auty 336-190 Engholm 29-15557 Mauerer 29-1555 Elmen 29-15561 Lilly 174-34 XR Strock 336-190 XR Tibbetts 29-15557 WHITMORE A. WILTZ, Primary Examiner. ELI J. SAX, JOHN F. CAMPBELL, Examiners. 

